Being accompanied with developing blue light emitting diodes (LEDs), the LEDs are recently used for light sources of displays or traffic signals and furthermore become to be used in place of incandescent lamps or fluorescent lamps. As it is preferable that the LEDs can be operated simply with AC driving of 100 V or the like in case that the LEDs are used in place of the incandescent lamps or the fluorescent lamps, as shown, for example, in FIG. 8, a structure in which the LEDs connected in series and/or parallel are connected to an alternative current power source 71 is known well. Here, S represents a switch (cf. for example PATENT DOCUMENT 1).
PATENT DOCUMENT 1: Japanese Patent Application Laid-Open No. HEI10-083701 (FIG. 3)